On 21 march 1963 the Presidium of the Communist Part of the USSR decided to drastically shorten the Vostok program in favor of the Voshkod program, which would develop a multi crew vehicle. Of the planned ten mission only six were performed. The missions that were cut from the program mostly consisted of high altitude solo mission researching the lower Van Allen belt, but also a dual female flight, Vostok 5/6, was cut from the program.
Tereshkova would pilot Vostok 5, while Valentina Ponomaryova (first image) would pilot the Vostok 6. Due to the cut in mission it was decided however that it would be a male/female mission, with Bykovsky piloting Vostok 5. Eventually only Tereshkova was aloud to fly because of propaganda reasons:
Although a final decision would only be made at the last minute, cosmonaut chief Kamanin always planned to name Tereshkova for the first flight. She was appropriately feminine and modest, and always mouthed the correct Communist party line in interviews. Ponomaryova was considered the most qualified candidate technically and emotionally for the Vostok 6 flight. However her aggressive feminism and failure to mouth Soviet catch-phrases were considered drawbacks by the male Communist stalwarts that ran the programme.Source: Encyclopedia Astronautica
Valentina Ponomaryova and backup cosmonaut Yorkina (second image) were never selected again to fly a mission.
In honor of Women’s Day, here are two all female crews that were planned, but never made it to reality.
Voskhod 5 (1966): intended to be a 10 day mission with a spacewalk. Included the other four women selected in the first female group: Valentina Ponomareva and Irina Solovyova as the prime crew, with Tatyana Kuznetsova and Zhanna Yorkina as their backups. Cancelled after the death of Chief Designer Sergei Korolyov in 1966.
Visiting Mission to Salyut 7 (1986): was to have a crew of Svetlana Savitskaya (she made the first female spacewalk in 1984), Yekaterina Ivanova and Yelena Dobrokvashina. Cancelled after Salyut 7 started to have problems.